Calcium manganite as oxygen electrode materials for reversible solid oxide fuel cell
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For an efficient high-temperature reversible solid oxide fuel cell (RSOFC), the oxygen electrode should be highly active for the conversion between oxygen anions and oxygen gas. CaMnO3-δ(CM) is a perovskite that can be readily reduced with the formation of Mn3+ giving rise to oxygen defective phases. CM is examined here as the oxygen electrode for a RSOFC. CaMn0.9Nb0.1O3-δ (CMN) with Nb doping shows superior electric conductivity (125 S cm-1 at 700 ºC) to CM (1-5 S cm-1 at 700 ºC) in air and is also examined for comparison. X-ray diffraction (XRD) data show that CM and CMN are compatible with the widely used yttria-stabilized zirconia (YSZ) electrolyte up to 950 oC. Both materials show a thermal expansion coefficient (TEC) close to 10.8-10.9 ppm K-1 in the temperature range between 100-750 ºC, compatible with that of YSZ. Polarization curves and electrochemical impedance spectra for both fuel cell and steam electrolysis modes were investigated at 700 ºC, showing that CM presented a polarization resistance of 0.059 Ωcm2 under a cathodic bias of -0.4 V while CMN gave a polarization resistance of 0.081 Ω cm2 under an anodic bias of 0.4 V. The phase stability up to 900 ºC of these materials was investigated with thermogravimetric analysis (TGA) and variable temperature XRD.
Ni , C & Irvine , J T S 2015 , ' Calcium manganite as oxygen electrode materials for reversible solid oxide fuel cell ' Faraday Discussions . DOI: 10.1039/C5FD00026B
Copyright 2015 the Authors. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/).
The authors thank EPSRC for funding under the contract of H2FC hub EPSRC: EP/J016454/1 and Platform EPSRC: EP/K006800/1 and JTSI thanks Wolfson Merit of Royal Society: WRMA 2012/R2
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